We have developed sensitive and specific radioimmunoassay systems for measurement of neurohypophysial peptides (NHP) including arginine vasopressin (AVP), vasotocin (AVT), and oxytocin (OT), and have standardized stimulus response test systems for assessing maturation of osmoreceptor, volume receptor and nociceptor control of hormone secretion. We will apply these techniques to a comprehensive study of maturation of control of AVP and AVT secretion in the fetus. In addition, we will characterize placental transfer of NHP and maturation of interaction with the renin angiotensin system. We will study maturation of renal receptor binding, NHP receptor specificity, and the possible role of NHP in inducing receptors. Finally, the maturation of receptor and non-receptor clearance of NHP and the possible role of NHP in regulating renal water excretion and placental water flux will be investigated.